Michelle obama is extremely popular on the internet tonight, after a dance performance that is a long way from the formality and reserve of past first ladies. Here's david kerley. Reporter: The first lady has gone viral. Mrs. Obama joined a dressed-in-drag jimmy fallon for what he called the evolution of mom dancing. Yes, go shopping, get groceries, raising the roof, even a bit of hip bumping. Come comedy, but the first lady has a reason to bust a move. Time has changed from the reserve shown by jackie o. First ladies have room to move. The first lady is dancing to promote her battle against childhood obesity, called let's move. Things like go outside, throw a ball, doing a little dancing, you can really make some significant improvements with small changes. Reporter: After dancing with the first lady, fallon, learned mrs. Obama has a quick wit. I said it here first, dream team michelle and hillary '16. What do you think? You know, I have my eye actually on another job. And I hear that when jay leno retires -- Reporter: But even fallon knows when to call it quits, as the first lady does the dougie. David kerley, abc news, washington. Michelle obama is a far cry from sarah polk who was the FIRST LADY IN 1940s. IN 1840s BANNED ALL DANCING AT The white house.

This transcript has been automatically generated and may not be 100% accurate.

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